What if someone from a distant star wanted to communicate with us? In this guest post my friend and avid reader David Keir lays out the history of the search for extra-terrestrial intelligence (SETI). In my postscript I'll delve deeper into the prospects of finding extra-terrestrial life and end with some thoughts about interpretation of messages of unknown origin.
Kreeno wenis. Plate of a collagraph print.
Space and the SETI Endeavour
by David Keir
Russia put into orbit the first ever man-made satellite, Sputnik, the year I was born (1957). This shocked the US into ramping up their efforts to get into space and try to out-match the Russians. In the event it was the US who put men on the moon before the 1960s ended. In those times there was no mainstream belief that extra-terrestrial life existed – despite the David Bowie hit song that asked "is there life on Mars?". As a kid growing up during the space-race and the Cold War, I got interested in Astronomy. The accepted truths then were:
We have found no evidence of life on planets in our own solar system;
Although we know there are countless billions of other stars, we will never know if they have planets or not.
By the turn of the 20th century all this landscape had changed. Not only did mankind now know that there were many planets orbiting other stars, but it was becoming likely that virtually all the stars in our own galaxy – and those in galaxies beyond – have their own planets. The odds that places exist, or existed, somewhere in the visible universe, with conditions favourable for life, had become close to certainty.
But is there actual life elsewhere? We still don't know.
In the last few years – especially since we now have a number of telescopes (visible light, infra-red, and radio-telescopes) actually situated in space itself, it has now become possible to detect things that would have been unimaginable in the 1960s. Not only is it now feasible to detect radio or other light-speed emissions from far away and weak sources, but it is now possible to detect the traces of technological activity on planets of distant stars (for instance the spectral signatures of chemicals that would not occur naturally in the atmosphere of distant "exo-planets".
All this means that the Search for Extra Terrestrial Intelligence (SETI) has transformed into something of growing concern worldwide.
SETI is not an organisation as such, but a term for the field of these endeavours. It has a long and chequered history; having been championed by cranks and dreamers on the one hand, to being endorsed by the likes of Carl Sagan and Steven Hawking on the other. SETI activities have at times been funded by governments (NASA for instance). Most recently a multi billion dollar project, called Breakthrough Listen has been launched – using existing radio-telescope dishes on the Earth, to search the skies diligently for any incoming signals. The problem is that there is the whole sky in all directions to search; and there are a very large number of wavelengths to look in.
Mostly no evidence has yet emerged of aliens – or of life of any kind other than what we know on our own planet. But there have been "occurrences." Some of the most famous are:
The Wow Signal of 1977 (a strong narrowband radio signal detected by Ohio State University's Big Ear radio telescope in the United States,
The detection, in 2008, of a long, thin object passing the Earth from deep space – dubbed Omouamua. (See the book written about this by Avi Loeb)
Breakthrough Listen Candidate objects; currently in the news due to Breakthrough Listen re-examining some of the SETI@Home results. (That was a scientific experiment, based at UC Berkeley, that crowd-resourced private owners of Internet-connected computers in the Search for Extraterrestrial Intelligence).
And there is a long history of individuals and groups who have tried to send signals out for ETIs to receive. Calling cards from Earth. Without any international consensus.
And, of course, we have been leaking electro-magnetic signals out into space since the invention of radio and television.
There is not the scope here to go into all these aspects, but the reader can easily pursue the historical accounts of these things, if interested. Absolute truth though, may be hard to find.
Most modern thinking on the SETI front has realised that, because looking far away means looking across millennia of time, civilisations could have evolved, thrived and died out – long before we started looking. However, the possibility of post-biological life (robots/AI essentially) continuing to exist for far longer, must be borne in mind.
A key point in all this is that our current science tells us that nothing can travel faster than light/radio waves across space. The nearest star to our sun is Proxima Centauri, and that is several light-years away. So any signal even from that nearest system would take several years to get to us. Actual space ships – even if they could reach near light-speed would have to accelerate and decelerate so gradually that a trip between Proxima Centauri and Earth would likely take multiple human lifetimes.
So we are safe... Unless there is some way (that we don't yet know of) to cross vast distances in an instant. Many physicists do not rule this out either.
Science Fiction has had a lot to say about all these issues – and Science Fiction has many times become science fact – you just have to wait long enough.
My own personal interest is in so-called "Post Detection" studies. Looking at possible types of detection (real ones, mistakes, misunderstandings and hoaxes) and trying to assess the types of societal, governmental and international reactions that might occur. The risks to humanity are not restricted to the fear of an invasion fleet from Planet Zog; we are quite capable of initiating home-grown disasters, as even a cursory look at modern human history tells us. To this end, I joined the SETI Post-Detection Hub – which is an initiative of the UK SETI Research Network, based at St Andrews University in Scotland.
Finally I must mention the Sign in Space project. Led by Daniella de Paulis, Artist in Residence at the SETI Institute in California, with enormous help from the European Space Agency, and involving some of my close colleagues in UK SETI. This "simulation of first contact" involved the transmission of radio waves (from a spaceship orbiting Mars) containing a carefully-thought-out package of information. The signal was captured by two radio telescopes on Earth and those data files were made available to the public. The challenge was thrown out to the public to try and interpret it, being creative and artistic if so inclined. At this point, a year on, an ingenious and determined father daughter team has decoded the signal (using techniques which are beyond the scope of my understanding or pay grade).
Postscript
by Risto Holopainen
In popular imagination a rather definitive image has emerged of what extra-terrestrials should look like. Hominids with large oblong heads and oversized dark eyes, as witnessed, among many places, in the Alien Autopsy video – which "the government doesn't want you to see" as the click-bait description usually says. The anthropocentric bias is evident. Intelligent life is easiest to imagine as resembling our own species or other species not too distantly related on the tree of life. The generic alien looks like an extrapolation resulting from a comparison of humans with other primates. Yet we know that corvids, dolphins, whales, elephants, dogs, and even squids are also capable of clever behaviour. It is therefore not surprising to find among the people involved in the SETI project a few biologists interested in animal communication. Recent efforts towards a classification of whale song phonetics has revealed it to be richer and more articulate than previously thought. Overhearing a bit of the intimate chatter of magpies should raise the suspicion that we have no clue what they are telling their close ones. So what hope could we possibly have of understanding a message of extra-terrestrial origin?
The animal kingdom is where we look for examples of intelligent life. I think most of us have difficulties conceiving of intelligent life bereft of sensory organs for vision and hearing, motility, and organs with which the organism can manipulate its environment. A brain would seem to be a prerequisite. It would take an original science-fiction writer like Stanisłav Lem to come up with a conception such as the Matmos, the apparently sentient ocean that covers the surface of an entire planet. The kingdoms of fungi and protists, including the fascinating Physarum Polycephalum (slime mold), should not be overlooked as prototypes for complex forms of life which, should they develop something we could identify as intelligence, would be extremely different from that of any animals we know of.
Drake's Equation and the Great Filter
We don't know how likely it is that we will ever receive a signal of alien origin. Nevertheless, there is an equation for this probability: Drake's equation is a check list of necessary conditions in the form of a series of variables.
N is the number of civilizations in the Milky Way from which we might, theoretically, receive some signal indicating intelligent life. This could be the equivalent of On Kawara's famous piece of conceptual art, the telegram saying "I'm still alive." The factors that determine N are, in order:
The rate of star formation
Fraction of stars with planets
Average number of planets per star that might be able to support life
Fraction of planets that could support life where life actually develops
Fraction of planets with any form of life that develops into intelligent life (civilisations)
Fraction of civilisations that develop technologies that emit detectable signs of their presence
The timespan during which such a civilisation emits detectable signals
One might think that the star formation rate R should be balanced by the death rate of stars, but this is implicit in the variable L, the time for which signals are emitted. The time an advanced civilization exists is supposedly limited by the star's lifetime.
Most of these variables are unknown, in practice only open to speculation and impossible to estimate. The rate of star formation in the Milky Way is reasonably well known, estimated to about 1.5–3 per year. As more exo-planets are discovered the fraction of stars with planets can also be estimated. But when it comes to potentially life supporting planets and the possible emergence of intelligent life we have only one example, our own planet and our own species. (Humans are evidently among the most intelligent species on Earth, but also, it seems, one of the most irrational, superstitious, unwise, and delusional species.)
Drake's equation offers significant room for biases and projection of pet theories. As we reason about hypothetical alien life and civilisation we have no choice but to draw on our own biology, history, and technology. Ultimately, all speculation about alien intelligent life turns into a more or less conscious self-scrutiny. What are the chances of survival when we have invented the means of destroying a significant part of all life on Earth including ourselves, either rapidly or slowly? Will we develop fleets of small self-replicating autonomous machines that spread out to colonise our corner of the galaxy?
Since there are so many stars in our galaxy, a fraction of which are now known to host planets within a potentially life-supporting distance, the question is: Where are everybody? Why have we not been contacted yet? (Leaving aside the fascinating folklore of close encounters and government cover-up.) This question is known as the Fermi paradox.
The vast scale of interstellar distances must be taken into account. An electro-magnetic signal emitted from some distant planet expands in all directions with the speed of light, similar to an expanding soap bubble. The thickness of this bubble depends on L, for how many years the signal is emitted, hence the shell of the bubble is L light-years thick. The presence of such a signal would only be detectable on Earth during those L years when the shell of the bubble passes our region of space. Also, the signal would have to be incredibly strong, or bright in terms of visual light, to be detectable several light-years away.
Other explanations of the radio silence from supposed intelligent co-inhabitants of distant space involve the scarcity of planets with conditions suitable for life to develop, a low probability of simpler organisms developing higher intelligence, and an unlikely transition from intelligent life forms to advanced civilisations that develop technologies on a scale and energy intensity sufficient to be detectable. According to the Great Filter theory it might also be that the period L is typically short. Advanced civilisations might exist at various locations for a brief moment, before they inevitably destroy themselves.
Here we see how the optimism or pessimism of a person reflecting on the possibility of alien life might influence their estimation of some factors of Drake's equation. For the techno-optimist there is no doubt that we will colonise space, which implies that others almost certainly have done so too. On the other hand, even the most cheerful collapsologist will note that the time window during which we might either send or receive messages through space is rapidly closing in. Yves Cochet, for example, argues that we have at most ten years before our civilisation collapses. There are things that can be done to escape the worst disasters, like replacing finance capitalism with degrowth, but there are many obstacles, such as human psychology (no-one likes to listen to an "alarmist" or voluntarily abstain from the conveniences of consumerism) and the politico-economic system which is too robust against profound change.
I hope to have made the case that we are probably wasting our efforts to find messages from extra-terrestrial sources, although I don't count on having persuaded firm believers. Nonetheless, much creativity goes into speculation about how to decode messages, should they arrive, and this can be interesting in itself. I recall one example of a hypothetical message coded in a binary set of symbols, let's say a short and a long bleep as in Morse code. In order to make sure the message is correctly received it is repeated a few times. As the story goes, at first the researchers find no meaningful pattern, then by chance they pay attention to the number of symbols in the message, let's say it is 899 symbols long. Could that be significant in some way? After a while someone notices that 899 = 29x31. What if the message is arranged as a two-dimensional grid of black and white dots? They decide to try this, and there it is. An alien selfie pops out. Or maybe a diagram showing what molecules their life form is based on.
Our propensity for pareidolia should always be kept in mind when trying to decode signals which we don't know, a priori, whether they are real messages or merely random noise. Pareidolia has to do with our tendency to recognise familiar shapes in random fluctuations, often illustrated with the image of a ”face” on the surface of Mars, resulting from the way a rock happens to cast a shadow. Since the human brain has an area dedicated to face recognition it is no wonder that we see faces in all kinds of places where there are none. Over-interpretation is always a risk when we listen to signals from space. Similarly, our willingness to find more meaning than there really is in a work of art, or other meanings than the artist may have envisioned, is also to blame for some excesses of art history and criticism.